1. Field of the Invention
The present invention relates to a microactuator for an optical switching operation of an Optical Cross Connect (OXC) and, more particularly, to an electrostatically-driven microactuator of an improved structure which is fabricated by a Micro-Electro Mechanical System, and is capable of accurately switching an angle of an optical path while being driven by a low voltage.
This application is based on Korean Patent Application No. 2000-57516, filed Sep. 29, 2000, which is incorporated herein by reference in its entirety.
2. Description of the Prior Art
Generally, a microactuator of an Optical Cross Connect (OXC) switches an optical path of an incident ray by adjusting an angle of a reflector. The electrostatically-driven microactuator usually drives the reflector by using a Scratch Drive Actuator, or a Comb Drive Actuator. There also is a microactuator which drives the reflector without using any actuators, by using the reflector as an electrode for generating an electrostatic force with another electrode disposed below the reflector.
However, the above first and second ways of driving the reflector, i.e., the methods that use the Scratch Drive Actuator or Comb Drive Actuator, have shortcomings. Since a separate actuator is required to drive the reflector, the volume of a chip increases, while the optical path is lengthened and an optical efficiency is deteriorated. The third way of driving the reflector, using the reflector as an electrode for generating an electrostatic force, may overcome these shortcomings, since it does not require any actuators to drive the reflector.
FIG. 1 shows a microactuator for directly driving a reflector. As shown in FIG. 1, the microactuator includes an upper electrode 1 and lower electrode 2 having a hole formed therein, and a reflector 3 pivotally supported on a supporter at the same height as the upper electrode 1. The reflector 3 is an Au-coated Poly-Si, which serves as an electrode. When a predetermined voltage is applied between the upper and lower electrodes 1 and 2, electrostatic force is generated between the reflector 3 and the lower electrode 2, and the reflector 3 is pivoted downward by an angle of 90xc2x0. Accordingly, the optical path of an incident of ray from an input optical fiber 4 is switched by 90xc2x0, and the ray of light is transmitted to an output optical fiber 5.
Although the volume of the chip is not increased, due to an omission of a separate actuator, there still are problems. That is, the fabricating process is complex, and a high voltage is required to drive the reflector 3. Another problem is that the ray of light experiences loss when transmitted from the input optical fiber 4 to the output optical fiber 5 unless the reflector 3 is pivoted to an angle of 90xc2x0 exactly. This means a complex structure since a separate device, such as a stopper, should be employed for an accurate pivoting movement of the reflector 3.
The present invention has been made to overcome the above-described problems of the related art, and accordingly, it is an object of the present invention to provide a microactuator which is driven by a low voltage and is capable of accurately pivoting a reflector to an angle of 90xc2x0 without having to use a separate device, and a fabricating method of the same.
The above object is accomplished by a microactuator according to the present invention, including a wafer; a lower electrode formed on an upper surface of the wafer; a side electrode formed on the upper surface of the wafer in a perpendicular relation with the lower electrode; a pair of supporting posts protruding from the upper surface of the wafer, spaced from the lower electrode at a predetermined distance, respectively; a reflector spaced from the side electrode at a predetermined distance, and facing the lower electrode; and elastic means disposed between the reflector and the supporting posts, said elastic means elastically supporting the reflector and enabling pivoting movement of the reflector.
Here, the elastic means is a pair of torsion springs. The reflector is divided by a fulcrum line into one side facing the lower electrode and an other side which is longer than the one side. It is preferable that the longer other side of the reflector have a hole formed therein for minimizing the level of electrostatic force applied to the side electrode.
The above object is also accomplished by a method for fabricating a microactuator according to the present invention, including the steps of forming a lower electrode, a side electrode base and a post-base by laminating a seed layer on a wafer and then etching the seed layer forming a pattern thereon; forming a coating frame by laminating a thick photo-resist layer on the wafer and the patterned seed layer and etching the thick photo-resist layer; forming an insulating film within the coating frame and etching the insulating film by exposing the side electrode base; laminating a side electrode on the side electrode base; laminating the photo-resist layer on the side electrode and the coating frame; forming a post-hole in the coating frame and the photo-resist layer by exposing the post-base; forming a reflector, torsion springs and supporting posts by laminating a metal layer on the photo-resist layer and the post-hole and then etching the metal layer; and eliminating the thick photo-resist layer and the photo-resist layer.